Conventional office chairs are designed to provide significant levels of comfort and adjustability. Such chairs typically include a base which supports a tilt control assembly to which a seat assembly and back assembly are movably interconnected. The tilt control mechanism includes a back upright which extends rearwardly and upwardly and supports the back assembly rearwardly adjacent to the seat assembly. The tilt control mechanism serves to interconnect the seat and back assemblies so that they may tilt rearwardly together in response to movements by the chair occupant and possibly to permit limited forward tilting of the seat and back. Further, such chairs typically permit the back to also move relative to the seat during such rearward tilting.
To control rearward tilting of the back assembly relative to the seat assembly, the tilt control mechanism interconnects these components and allows such rearward tilting of the back assembly. Conventional tilt control mechanisms include tension mechanisms such as spring assemblies which use coil springs or torsion bars to provide a resistance to pivoting movement of an upright relative to a fixed control body, i.e. tilt tension. The upright supports the back assembly and the resistance provided by the spring assembly thereby varies the load under which the back assembly will recline or tilt rearwardly. Such tilt control mechanisms typically include tension adjustment mechanisms to vary the spring load to accommodate different size occupants of the chair.
It is an object of the invention to provide an improved tilt control mechanism for such an office chair.
In view of the foregoing, the invention relates to an office chair having an improved tilt control mechanism which controls rearward tilting of the back assembly relative to the seat assembly.
The tilt control mechanism of the invention incorporates a tension adjustment mechanism which cooperates with a pair of coil springs that defines the tilt resistance being applied to the chair uprights. The tension adjustment mechanism includes a cam block movably supported on the control body which slidably engages a pair of spring legs of the coil springs. The cam block has an arcuate cam surface which cooperates with the spring legs wherein the cam block is driven sidewardly to move the spring legs upwardly or downwardly to respectively increase or decrease the spring load being applied by the coil springs to resist rearward tilting.
The cam block is mounted on a threaded drive shaft which shaft extends laterally across the tilt control mechanism and is rotatably supported on the control body. The end of the drive shaft extends to an end of the cam block wherein rotation of the drive shaft causes the cam block to reversibly move sidewardly beneath the spring legs, wherein the arcuate cam surface supporting the spring legs thereby controls displacement of the legs upwardly or downwardly depending upon the direction of movement of the cam block. In particular, the spring legs may move upwardly to increase tilt tension, or downwardly to reduce the tilt tension. This mechanism provides an improved tension adjustment mechanism that is easier to actuate for the occupant.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.